I just ordered the 128 GB model and will be "downgrading" from my 256 (current) SSD to it. For my needs, the extra space is irrelevant, and most of my large files (i.e. media) is all on external devices anyway, so putting that $200 towards something else is better.
It really depends on the needs of the user though. Personally speaking, I don't think 256 is sufficient for the "average" user either, assuming that don't stream all of their media (which is increasingly becoming the case), but that's just me. 256 is good for those who boot camp (for gaming) though, and for those with multiple VMs, assuming the OS is large.